1. Field of the Invention
The present invention relates to a matrix type ultrasonic probe constructed by arranging a plurality of piezoelectric elements in two-dimensional directions and a method of manufacturing the same. More particularly, it relates to a matrix type ultrasonic probe provided with a plurality of minute piezoelectric elements and a method of manufacturing the same.
2. Description of the Related Art
The ultrasonic probe is used as a unit for transmitting and receiving an ultrasonic wave in ultrasonic diagnostic equipment for a medical purpose and so on. In recent years, for example, as Japanese Laid-open Patent Application No. 2000-41299 (JP, P2000-41299 A) discloses, a matrix type ultrasonic probe in which a plurality of piezoelectric element are arranged in two-dimensional directions has come into notice. When the matrix type ultrasonic probe is applied to an examinee, i.e., a living organism, a stereoscopic picture can be obtained in real time as in vivo information.
As shown in FIG. 1, the matrix type ultrasonic probe according to the background art mostly has been provided with such a construction that a plurality of piezoelectric elements 2 are disposed in two-dimensional directions on backing material 1. Backing material 1 has a surface thereof onto which mounts or pedestals 3 made of, for example, resin are secured. Mount 3 is provided for every piezoelectric element 2, and is interposed between piezoelectric element 2 and backing material 1. In backing material 1, a plurality of strip-shape signal lines 4 is embedded. One end of signal line 4 is exposed on the surface of mount 3, and the other end of each signal line 4 is led out of the back of backing material 1. Each piezoelectric element 2 has, on upper and lower faces thereof, electrodes 5a and 5b, respectively. Each piezoelectric element 2 is fixedly secured to the surface of mount 3 by conductive adhesive (not shown), whereby signal line 4 exposed on the surface of mount 3 is electrically connected to lower electrode 5b of piezoelectric element 2.
Next, a description of the manufacturing method of such matrix type ultrasonic probe according to the background art will be provided with reference to FIG. 2. To begin with, a plurality of pectinate metallic thin plates 7, each being formed in a comb by combining ends of strip-shape signal lines 4 with connecting member 6 are prepared, and these metallic thin plates are embedded in backing material 1 in a parallel state. Onto the surface of backing material 1, a resin plate 3A to be formed in mounts 3 is fixedly secured beforehand by adhesive. At this time, connecting members 6 of metallic thin plates 7 are arranged so as to be exposed on the surface of resin plate 3A. Then, on the surface of resin plate 3A, piezoelectric plate 2A preliminarily provided, on opposite faces thereof, with electrodes 5A and 5B, respectively, is fixedly secured by conductive adhesive. Resin plate 3A and piezoelectric plate 2A are respectively shaped to have an extent substantially corresponding to the two-dimensional matrix of a plurality of piezoelectric elements 6.
Thereafter, slits 8 (refer to FIG. 1) reaching backing material 1 from the upper surface of piezoelectric plate 2A is provided for cutting piezoelectric plate 2A, resin plate 3A and connecting member 6 so as to form a plurality of piezoelectric elements 2, and mounts 3A and signal lines 4 for every piezoelectric plate 2. As a result, plural piezoelectric elements 2 arrayed in two-dimensional directions and having signal lines 4 led out of lower face electrodes 5b are acquired. In each slit 8, non-illustrated filler is applied. Upper face electrodes 5a of respective piezoelectric elements 2 are commonly connected to one another by metallic film formed by the method of deposition or the like, and are grounded to the earthing potential. Thus, the matrix type ultrasonic probe as shown in FIG. 1 is completely manufactured.
By the way, in order to increase the resolution of such matrix type ultrasonic probe, reduction in the size of piezoelectric element 2 has been brought into practice. For example, reduction in the planar size of each piezoelectric element 2 to approximately 0.2 mm×0.2 mm has been tried. When it is assume that the oscillating frequency of such piezoelectric element 2 is, for example, approximately 2.5 MHz, the corresponding thickness (height) of piezoelectric element 2 would reach 0.6 mm, and accordingly, the height of piezoelectric element 2 must be appreciably large in comparison with the width thereof. Therefore, during the manufacturing process, when piezoelectric plate 2A is severed or divided by cutting into piezoelectric elements 2, securing strength by the conductive adhesive is rather small, so that piezoelectric elements 2 are apt to be fallen. Thus, a problem occurs such that piezoelectric elements 2 fail to be arranged in position on backing material 1.